This invention relates generally to portable apparatus for freezing the liquid contents of pipes for working on the pipe, and to the more particular field of portable pipe freezers that use a refrigerant cycle for cooling the pipe.
Pipe freezers are used in repairing or replacing pipe sections or repairing or adding fittings. When there is no convenient shut-off valve, the effect of blocking flow in the pipe can be achieved by freezing the water in a section of the pipe. The frozen section acts as an ice plug that blocks flow.
Some pipe freezer devices use frozen CO2 (dry ice) for the heat transfer to freeze the section of pipe. This invention however, relates to devices that use a refrigerant in a refrigeration cycle for the heat transfer. Such devices are described, for example, in U.S. Pat. No. 5,548,965. The same patent describes an evaporator head with multiple channels sized to fit various standard pipe diameters. Two evaporator heads are connected to a portable condenser/compressor unit by flexible coaxial tubes that cycle refrigerant to and from the evaporation chambers.
This invention improves upon the pipe freezer of U.S. Pat. No. 5,548,965 by structural differences that make it easier to install the evaporator heads in some situations and internal structural differences that improve the evaporation heat exchange.
The invention is in an apparatus for freezing the contents of a pipe through the use of a refrigeration cycle. The apparatus includes a portable condenser/compressor unit and a pair of flexible coaxial hoses connected to an evaporation chamber. A set of interchangeable adapters configured with one or more nearly semicircular channels conforming to a standard pipe diameter are used to place the evaporation chamber along and in heat transfer conduction with a section of a pipe. The adapters are configured to hold the evaporation chamber in a position such that the length axis of the chamber is aligned parallel to the axis of the pipe. The evaporation chamber has its hose coupling located approximately midway along its length dimension and is oriented perpendicular to the length axis of the chamber. This angle of connection into the adapter makes it easier to install when the pipe is close to a wall or structure that interferes with the hose being parallel to the pipe. Inside the chamber, a baffle placed between the outlet of the inner tube of the hose and the return to the outer tube forces refrigerant sprayed out of the inner tube to migrate from essentially the midway point of the chamber to an end wall and then back toward the midway point before entering the outer tube. This migration path allows more efficient evaporation in the chamber and thus more efficient heat exchange. In a preferred embodiment, the evaporation chamber is in the shape of a right cylinder closed by a pair of end plates. The chamber is constructed of a heat conductive metal, preferably aluminum. Also preferred is to protect the evaporation chamber from dents and scratches by installing over it a replaceable open cylindrical sleeve.